Question

I want to paint all three walls of the kitchen. One wall is half a cylinder. I want to paint the walls only, not the ceiling. The walls are 9' high. How many square feet will I be painting? Round to the nearest tenth.

Answer 1

335.5 sq ft.

Explanation:

Let's start with the 2 straight 10-feet long walls, it's easier.

Each of those two wall sections are 10 feet long by 9 feet high... They're rectangles, so their area is their base (10) by their height (9).

Wall 1 = 10 x 9 = 90 sq ft

Wall 2 = 10 x 9 = 90 sq ft

Now the half-circle portion.

The trick here is to calculate half of the circumference. The circumference of a circle is given by C = 2 π r, but we only want half of it... so C/2 = π r

We have the radius (r = 5.5 ft).

So, the half circle has a (half) perimeter of: 5.5 π r = 17.28 ft

Then we multiply this by the height of 9 feet: 17.28 = 155.52 sq ft

Then we add the two other walls:

Total area = 90 + 90 + 155.52 = 335.52, which we round down to 335.5 sq ft.